This invention relates generally to clutch mechanisms for tools.
Referring to FIG. 1, a circular saw blade 10 is normally driven by a rotating arbor 20 operatively connected to a motor (not shown) of a power tool. In many applications, the blade 10 has a circular hole 11 through the center for acceptance of the arbor 20. The arbor 20 may often have a smaller diameter mounting portion 21 which extends from a larger primary portion of the drive arbor to form a shoulder 22. The blade 10 is typically placed over the smaller diameter mounting portion 21 until it is stopped against the shoulder 22 formed by the main drive portion of the arbor 20. The blade 10 is then locked on to the arbor by clamping it between the shoulder 22 and either a threaded locking nut 23 which is threaded onto the end of the small diameter mounting portion 21 (see, e.g., U.S. Pat. Nos. 5,477,845 and 5,303,688) or a bolt threaded into a threaded hole in the end of the arbor (see, e.g., U.S. Pat. No. 5,303,688). Sometimes, a blade clamp 24 may be disposed between the blade 10 and the shoulder 22. Similarly, a second blade clamp 25 and/or a washer 46 may be disposed between blade 10 and nut 23. The blade 10 then rotates with the arbor 20 because of the clamping force.
Sometimes because of the clamping force, the blade 10 may stop rotational movement of arbor 20 when blade 10 gets caught by a workpiece. Such lack of movement may damage the motor or gears connecting the motor to arbor 20.
In accordance with the present invention, an improved power tool is employed. A power tool includes a motor, an arbor driven by the motor, a rotatable cutting tool disposed on the arbor and having a rotational axis, the cutting tool further having a hole, first and second clamps connected to the arbor and clamping the blade, wherein one of the cutting tool and at least one of the first and second clamps and arbor have a first drive surface for contacting a second drive surface on the other of the cutting tool and the at least one of the first and second clamps and arbor, the second drive surface being movable between a first position contacting the first drive surface and a second position bypassing the first drive surface. The second drive surface is resiliently connected to the other of the cutting tool and the at least one of the first and second clamps and arbor. At least one metal strip connects the second drive surface to the other of the blade and the at least one of the first and second clamps and arbor.
Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below.